An ambulance whizzes by, and suddenly its siren drops in pitch. We are all familiar with the Doppler effect, even if we don’t know it by name. Now, scientists have found an alternative version of the phenomenon, for when sound, or light, scatters off a rotating object. The discovery could enable astronomers to measure a distant planet’s rotation, or even improve the performance of wind turbines.
Here’s how the Doppler effect works: When a noisy object is moving toward you, its sound waves bunch up, producing a higher frequency, or pitch. Conversely, as soon as the object is moving away from you, the sound waves stretch out, and the pitch lowers. The faster the object, the greater the pitch change.
The Doppler effect occurs for light as well as sound. For instance, astronomers routinely determine how fast stars and galaxies are moving away from us by measuring the extent to which their light is “stretched” into the lower frequency, red part of the spectrum. Redshifts like this were famously used in the 1920s to infer that most stars and galaxies are moving away from us and that the universe must be expanding.
Redshifts in light, and the pitch-drop of passing sirens, are examples of a linear Doppler effect. In recent decades, however, scientists have discovered that the Doppler effect also exists for objects that are rotating, the so-called orbital angular momentum (OAM) of light, and now researchers they believe they can determine how fast a planet is spinning.
Back on Earth, he adds, lasers that measure the OAM could be sent through wind farms to determine the rotation of air currents. “If you’re a windmill, you’d like to know in advance of blustery wind, so you can tether your blades.”
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Reported by JON CARTWRIGHT of ScienceNOW. This is adapted from ScienceNOW, the online daily news service of the journal Science. http://news.sciencemag.orgRead More
NASA’s Cassini spacecraft has captured stunning views of a monster hurricane at Saturn’s North Pole.
The eye of the cyclone is an enormous 1,250 miles across. That’s 20 times larger than the typical eye of a hurricane here on Earth. And it’s spinning super-fast. Clouds at the outer edge of the storm are whipping around at 330 mph.
The hurricane is parked at Saturn’s North Pole and relies on water vapor to keep it churning. It’s believed to have been there for years. Cassini only recently had a chance to observe the vortex in visible light.
Scientists hope to learn more about Earth’s hurricanes by studying this whopper at Saturn.
Cassini was launched from Cape Canaveral in 1997 and arrived at Saturn in 2004.
Reported by MARCIA DUNN of the Associated Press from CAPE CANAVERAL, Fla.Read More
An international team of astronomers has found two planets whose size and position suggest they may support alien life.
The planets orbit a star about 2,000 light-years away from Earth. The star is named Kepler-62. The planets appear to be the right distance from their star for liquid water. With the chance of water, there’s also a chance for life to exist, according to research published online Thursday by the journal Science.
Compared with Earth, the planets, named Kepler-62e and Kepler-62f, are larger and receive 0.41 and 1.2 times the amount of solar radiation. The planet hunters, led by NASA’s William Borucki, say they won’t know what the planets look like or if they are in fact habitable until they can study them a while longer.
“We have found two planets in the habitable zone of another star, and they are the best planets found to date” that may support life, said Borucki, a space scientist at NASA’s Ames Research Center in Moffett Field, Calif.
One of the planets, Kepler-62f, may be a rocky celestial body with polar ice caps, Borucki said. The other, Kepler-62e, is believed to be warm and have lightning. While it’s too soon to know for sure, it may even be a water world, the first of its kind discovered, Borucki said.
“Kepler-62e probably has a very cloudy sky and is warm and humid all the way to the polar regions,” Dimitar Sasselov, an astronomer at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., said. “Kepler-62f would be cooler, but still potentially life-friendly.”
Mission accomplished: The planets were discovered using NASA’s Kepler satellite, a spacecraft launched in 2009 with a mission to discover Earth-size and smaller celestial bodies in regions around their stars, particularly those where liquid water may exist. The spacecraft was launched in March 2009 and has found more than 2,700 planet candidates.
Kepler detects planets that cross the face of their stars, and gathers data that enables astronomers to estimate the sizes and make suggestions about composition.
The Kepler planets have 1.41 and 1.61 the radius of the Earth, according the researchers. Both planets may be solid, with either rocky or icy compositions, the scientists said.
In 2011, the Kepler mission found its first planet in the habitable zone, called Kepler-22b. That planet is larger than Earth, and orbits a sun-like star every 290 days.
Reported by EVA VON SCHAPER and ELIZABETH LOPATTO for Bloomberg News.Read More
It’s the Martian version of a spring break: Curiosity and Opportunity will take it easy this month because of the sun’s interference.
For much of April, the sun blocks the line of sight between Earth and Mars. This celestial alignment — called a Mars solar conjunction — makes it difficult for engineers to send instructions on the surface. The same problem also means that NASA can’t talk with rovers’ companion spaceships that orbit the Red Planet and help the space agency communicate with the Mars-roving robots.
Such communication blackouts occur every two years when the red planet disappears behind the sun. No new commands are sent since flares and charged particles spewing from the sun can scramble transmission signals and put spacecraft in danger.
Mission teams prepared by uploading weeks of scaled-back activities beforehand.
“They’re on their own,” said Rich Zurek, chief Mars scientist at the NASA Jet Propulsion Laboratory.
The rovers are banned from driving. Instead, they take a staycation and study their surroundings. The orbiting Mars Odyssey and Mars Reconnaissance Orbiter continue to listen for the rovers and make their own observations, but for the most part will transmit data once Mars is in view again.
Opportunity, Odyssey, Mars Reconnaissance Orbiter and the European Space Agency’s Mars Express have survived previous bouts of restricted communications. It’s the first for Curiosity, which landed last year near the Martian equator to hunt for the chemical building blocks of life.
The break continues through May 1. During that time, Curiosity can only check the weather every hour, measure radiation and look for signs of water below the desert-like surface. The limited chores are a departure for the active six-wheeler, which is used to driving, drilling and zapping its laser at rocks.
Scientists must wait until next month to drill into another rock and start the long-delayed trek to a mountain where Curiosity will search for the elusive organic molecules that are fundamental to life as we know it. The road trip was supposed to have started last year, but longer-than-expected science experiments put Curiosity behind schedule.
Odyssey, circling Mars since 2001, has experienced half a dozen blackout episodes with no problem. This time, it will try something new. There are plans to radio Earth every day even if calls are dropped, mostly to keep engineers updated on Curiosity’s health. The rover is also programmed to send daily beeps to ground controllers.
By contrast, the Mars Reconnaissance Orbiter will record and store information onboard its computers and beam it back after the hiatus. Opportunity, which parked itself in a clay-rich spot, will use the down time to study a rock and track the amount of dust in the sky.
With Mars missions on autopilot, many scientists and engineers planned to take vacation while a small crew remains on duty.
Reported by ALICIA CHANG of the Associated Press from Los Angeles, Calif. Follow her at http://twitter.com/SciWriAlicia.Read More
A Soyuz space capsule carrying an American astronaut and two Russian cosmonauts landed over the weekend on the foggy steppes of Kazakhstan, safely returning the three men to Earth after a 144-day mission to the International Space Station.
NASA’s Kevin Ford and Russians Oleg Novitsky and Yevgeny Tarelkin had been scheduled to return on Friday, but the landing was postponed by a day because of bad weather.
Live footage on NASA TV showed all three men smiling as they were helped out of the capsule and into reclining chairs to begin their acclimatization to Earth’s gravity after nearly five months in space.
A NASA TV commentator said only two of 12 search and rescue helicopters were allowed to land at the touchdown site because of heavy clouds and fog. So instead of being placed in an inflatable medical tent for checks, the astronauts were taken fairly quickly to one of the helicopters. The temperature at the time was well below freezing.
The crew was then flown to Kostanai, the staging site in Kazakhstan, where they posed for more photographs. Ford put on a traditional felt Kazakh hat and draped a matching coat over his flight suit, while holding up a matryoshka nesting doll of himself —- all souvenirs of the mission that began and ended in the Central Asian country.
The three men blasted off on Oct. 23 from the Baikonur cosmodrome, which Russia leases from Kazakhstan.
Vladimir Popovkin, the head of the Russian space agency, described the crew as “giving off good vibes, that they are a united and friendly team,” the Interfax news agency reported.
Space officials said Ford would be flown to Houston, while the Russians would return to the space training facility outside Moscow.
Their return voyage to Earth began with the Russian-made capsule undocking from the space station and beginning its slow drift away. The craft made a “flawless entry” back into the Earth’s atmosphere, descended through heavy cloud cover and landed perfectly in an upright position, the NASA commentator said.
Three other astronauts -— from Russia, the U.S. and Canada -— remain at the space station. The next three-man crew -— two Russians and an American -— is scheduled to launch from the Baikonur cosmodrome on March 29.
Reported by LYNN BERRY of the Associated Press from MOSCOW, Russia.